As a 17 year old, Taylor Lautner was able to easily add muscle mass by doing a good strength training routine and ensuring that he ate enough calories. There were a couple unique aspects of Taylor Lautner workout that allowed him to gain muscle mass:
Negative reps: he would focus on the downward motion of lifts to put extra strain on his muscles
Varied sets, reps, and weight: this prevented his body from adapting to his workout routine
Used giant rubber bands to create extra tension: he added these rubber bands to the free weights to force his muscles to work through a full range of motion
Taylor also knew that he should not overtain his muscles. He took every 3rd day off and never exercised more than 5 times per week. Despite his six pack, he didn't overtain abs either, merely training them 3 days per week by doing leg raises, planks, and reverse crunches.
